How to create bold, italic and underlined text
BBCode includes tags to allow you to quickly change the basic style of your text. This is achieved in the following ways:

You can select the text and then click on the icon box for the style you want from the choices in the styles list right under the subject line of you post.
OR
You can type in the codes yourself.. Here is a list of effect you can get-
Look here for instructions on how to do this-
http://www.phpbb.com/community/faq.php?mode=bbcode